Anisotropy beneath the Tibetan Plateau: A survey of shear wave splitting analyses

Open Access
Author:
Desser, Elizabeth M
Graduate Program:
Geosciences
Degree:
Master of Science
Document Type:
Master Thesis
Date of Defense:
November 02, 2011
Committee Members:
  • Charles James Ammon, Thesis Advisor
Keywords:
  • Tibet
  • anisotropy
  • shear wave splitting
Abstract:
One of the most impressive surficial features on Earth is the Himalayan-Tibetan orogen, comprising the Himalaya Range and the associated Tibetan plateau to its northeast. Diverse experiments have been conducted in Tibet in attempts to advance our understanding of the state of anisotropy in the upper mantle beneath the plateau. Results from previous studies of shear wave splitting on the Tibetan Plateau suggest several models of mantle lithospheric flow, such as the rotational flow patterns observed around the Eastern Himalaya syntaxis. I use the SplitLab processing environment to measure the shear wave splitting of teleseismic shear wave SKS and SKKS phases recorded on 386 broadband seismic stations within nine networks deployed across the Tibetan Plateau. I observe some strong variations in SKS splitting parameters across major terrane boundaries but also detect strong lateral variations in the SKS splitting in the west-to-east direction within both the Lhasa and Qiangtang terranes. In the Lhasa terrane, the apparent splitting decreases from west to east, in contrast with the Qiangtang terrane, which shows an eastward increase in SKS splitting. Patterns in much of the Himalaya and in southeastern Tibet are complex with rapid apparent changes in the overall SKS splitting parameters.